1. Field of the Invention
The present disclosure generally relates to wire bonding, and, more particularly, to techniques and devices for fabricating bonding wires.
2. Description of the Related Art
The manufacturing of integrated circuits involves many complex process steps to form circuit elements, such as transistors, capacitors, resistors and the like, in and above an appropriate semiconductor material. In recent years, enormous advances have been made in increasing integration density and overall functionality of the integrated circuits. These advances have been achieved by scaling the individual circuit elements to dimensions in the deep sub-micrometer range, with currently used critical dimensions, such as the gate length of a field effect transistor, of 30 nm and less. Hence, millions of circuit elements may be provided in a die, so that a complex connection fabric may also have to be designed, in which, typically, each circuit element may be electrically connected to one or more other circuit elements. These interconnect structures are typically established in a metallization system comprising one or more wiring levels, in which appropriate metal features are formed according to the circuit configuration under consideration, in a similar manner as a multi-level printed circuit board, wherein, however, the dimensions of the metal features have to be adapted to the dimensions of the semiconductor circuit elements, such as the transistors and the like.
In an advanced stage of the manufacturing of integrated circuits, it is usually necessary to package a chip and provide leads and terminals for connecting the chip circuitry with the periphery. Well-established approaches for connecting chips with a package include wire bonding techniques, which have been successfully developed over the last decades on the basis of aluminum and are still well established and represent the dominant technology for connecting the vast majority of semiconductor chips to a carrier substrate, wherein, usually, aluminum-based bond pads are provided, which are contacted by an appropriate wire made of aluminum, copper, gold and the like. During the wire bonding process, the bond wire is brought into contact with the bond pad and, upon applying pressure, elevated temperature and ultrasonic energy, the wire is welded to the bond pad to form an intermetallic connection.
In this manner, a reliable electrical connection may be established between the metallization system of the integrated circuit and any peripheral components, such as a substrate package and the like. Due to the ongoing shrinkage of feature sizes of sophisticated semiconductor devices, the complexity of integrated circuits may be continuously increased, thereby also requiring increased I/O (input/output) capabilities, which in turn necessitates an increased number of bond pads to be provided at appropriate positions, such as the chip periphery. Consequently, the size and also the pitch of the bond pads may be reduced, thereby requiring sophisticated wire bond techniques for positioning and connecting the bonding wire to the corresponding bond pads. For this reason, the diameter of the bonding wires may also have to be reduced to comply with the requirement for reduced lateral dimensions of the bond pads and also with respect to not unduly wasting valuable raw materials, such as gold and the like. Typically, bonding wires are formed by pulling a pretreated wire through a corresponding diamond crystal having formed therein an appropriate opening, the width of which substantially determines the desired target diameter of the bonding wire.
FIG. 1 schematically illustrates a schematic view of an apparatus 150 for providing a bonding wire having a desired target diameter. As illustrated, a material source 151 is provided, which may supply a preform 152 of a bonding wire, such as a gold wire, a copper wire, an aluminum wire and the like, the diameter of which may, however, not correspond to a desired diameter 152D. Furthermore, the apparatus 150 comprises a device 100 that is configured to act as a template when the preform 152 is pulled through an opening 102 that is formed in a body 101 comprised of a diamond crystal. Due to the interaction of the opening 102, which may act as a template, the preform 152 may be reduced to the desired target diameter 152D, thereby obtaining a bonding wire 152A that may be used for connecting to a bond pad, as is described above. When reducing the target diameter 152D, corresponding diamond crystals having respective openings 102 also may have to be formed, which is typically accomplished by drilling a corresponding hole into the diamond crystal body, thereby requiring sophisticated mechanical tools and techniques. Consequently, a precise control of the target diameter of sophisticated bonding wires may depend on the precision with which the corresponding template holes 102 may be formed in the diamond body 101. Consequently, changing the diameter of a bonding wire may be associated with significant efforts with respect to providing an appropriate device 100 based on conventional techniques involving the mechanical drilling of corresponding openings into a crystalline diamond body.
The present disclosure is directed to various methods and devices that may avoid, or at least reduce, the effects of one or more of the problems identified above.